Navigation method and navigation system for means of locomotion

ABSTRACT

A method for navigating from a starting point, especially from an instantaneous location, to a destination, a routing algorithm of a navigational system for a means of locomotion, particularly a motor vehicle, ship, or airplane, calculating a route from the instantaneous location to the destination via nodal points stored in a digital map. In the case in which at least one of the nodal points of the route to be calculated is not contained in an internal digital map stored internally in the navigational system, the part of the route which exclusively includes nodal points of the internal digital map is calculated by an internal routing algorithm on the basis of the internal digital map as an internally calculated route portion, and the part of the route which does not include nodal points stored in the internal digital map is calculated by an external routing algorithm as an externally calculated route portion on the basis of a digital map stored externally with respect to the navigational system, transitional nodal points from the externally calculated route to the internally calculated route and/or vice versa being determined.

FIELD OF THE INVENTION

The present invention relates to a method of navigating from a startinglocation, especially an instantaneous position, to a destination, arouting algorithm of a navigational system for an apparatus oflocomotion, in particular a motor vehicle, ship or airplane, calculatinga route from starting location to destination via nodal points stored ina digital map. The present invention also relates to a navigationalsystem for an apparatus of locomotion, especially a motor vehicle, shipor airplane, having an internal route memory, an internal navigationdevice connected to it, an internal digital map and a datacommunications device for communicating with an external off-boardnavigational system.

BACKGROUND INFORMATION

Navigational systems, such as those in motor vehicles, are based ondigital maps carried along in read-only memories. Since all functionalelements are located in the vehicle, these navigational systems areclassified as autonomous navigational systems. Navigational systems arealso known in which the routes are calculated outside the actual routeguidance system. For example, the route to be traveled by the vehiclemay be calculated in a traffic telematics center. These so-calledoff-board navigational systems have the advantage that the range of useis not limited right from the beginning by volume and state of updatingof the digital maps carried along. On the other hand, the speed,convenience and precision of an autonomous navigational system can onlybe achieved by a communications effort which is economically notfeasible at this time.

However, conventional navigational systems have the disadvantage thateither a completely autonomous route calculation takes place, or acompletely external or off-board route calculation takes place, eachhaving the disadvantages described above.

SUMMARY OF THE INVENTION

An object of the present invention is to make available an improvednavigation method and an improved navigational device of the kind namedabove, which will eliminate the disadvantages recited above.

To accomplish this, according to the present invention it is providedthat, in a navigation method of the type named above, in the case inwhich at least one of the nodal points of the route to be calculated isnot contained in an internal digital map stored internally in thenavigation system, the part of the route, which includes exclusivelynodal points of the internal digital map, is calculated by an internalrouting algorithm on the basis of the internal digital map as theinternally calculated part of the route, and the part of the route notincluding nodal points stored in the internal digital map is calculatedby an external routing algorithm on the basis of a stored digital mapthat is external with respect to the navigation system, as theexternally calculated part of the route, transitional nodal points fromthe externally calculated route to the internally calculated route,and/or vice versa, being determined.

This has the advantage that a hybrid navigation system is available, inwhich the detailed data of the internal digital map are used, as far aspossible, for the route guidance, and only in ranges lying outside theinternal digital map a route guidance is used on the basis of anexternally stored digital map. Thereby, according to the presentinvention, the advantages of an autonomous navigational system, namely,a high route guidance accuracy are unified with the advantages of anoff-board navigational system, namely, no range limitation based on thedigital map. At the same time, the disadvantages of an autonomousnavigational system, namely, conducting navigation exclusively withinthe internally stored map, as well as the disadvantages of an off-boardnavigational system, namely, high transmission costs due to the largedata volumes to be transmitted, are avoided. Thus, the user hasavailable to him the advantages of the “off-board” navigational systemand the autonomous navigational system under a uniform operating surfacehaving the best possible functions of each part.

In a preferred specific embodiment, the complete route is firstcalculated by the external routing algorithm, is transmitted to thenavigational system, and subsequently that portion of the route, whichincludes exclusively nodal points stored in the internal map iscalculated, and the corresponding portion of the externally calculatedroute is replaced by the internally calculated portion of the route.

In order to reduce communications costs and transmitting time, theinternal routing algorithm first generates the internally calculatedroute, transmits data concerning still missing portions of the route,especially still missing nodal points and interchange nodal points, tothe external routing algorithm, the external routing algorithmcalculates only the still missing route portions and transmits these tothe navigational system.

In a preferred specific embodiment, the internally calculated portion ofthe route is stored in the navigational system in an internal routememory, and the externally calculated portion of the route is stored inthe navigational system in an external route memory, whereby either aninternal navigation algorithm of the navigational system conducts aroute guidance based on the route in the internal route memory, or anexternal route guidance algorithm of the navigational system conducts aroute guidance based on the route in the external route memory.

Expediently, on reaching a transitional nodal point, switching takesplace from the internal route guidance algorithm to the external routeguidance algorithm when the apparatus of locomotion leaves the range ofthe internal digital map, or switching from the external route guidancealgorithm to the internal route guidance algorithm takes place when theapparatus of locomotion reaches the range of the internal digital map.

Actual data are attained at all times in the internal route memory aswell as the external route memory, if, during route guidance, nodalpoints already reached or passed sections of the route, are identifiedin the internal route memory as well as the external route memory astaken care of or passed, or are canceled, independently of which routeguidance algorithm just happens to be active.

For rapid assignment of nodal points to the internal map or the externalmap, and for rapid retrieval of the corresponding interchange nodalpoints, internal nodal points stored in the internal digital map as wellas external nodal points located outside the range of the internaldigital map are stored in a destination input memory of the navigationalsystem, and at least one interchange nodal point is stored forpredefined external nodal points, the interchange nodal point being aninternal nodal point contained in the internal digital map.

In order to optimize the selection of the interchange nodes, theinterchange nodal points are determined in a separate communicationsstep between the navigational system and an off-board navigationalsystem, which executes the external routing algorithm and stores theexternal digital map, using a data protocol in the light of geographicaldescriptions of nodal points lying outside the internal digital map.

In one advantageous specific embodiment, after the input of adestination lying outside the range of the internal digital map, thenavigational system transmits the input destination and a version numberof the internal digital map to an off-board navigational system, whichexecutes the external routing algorithm and stores the external digitalmap, from which the off-board navigational system determines aninterchange nodal point from these data, going from which to the inputdestination the externally calculated portion of the road is calculatedby the external routing algorithm and transmitted to the navigationalsystem.

Expediently, the navigational system transmits a list of possibleinterchange nodal points to an off-board navigational system whichcarries out the external routing algorithm and stores the externaldigital map, the off-board navigational system selecting at least onesuitable interchange nodal point according to the externally calculatedportion of the route and transmitting it to the navigational systemalong with the externally calculated portion of the routs.

In another preferred specific embodiment the calculation of theexternally calculated portion of the route occurs when the apparatus oflocomotion leaves an area of the internal digital map.

In a navigational system of the type named above, the present inventionallows for an external route memory connected to a data communicationsdevice as well as an external route guidance device connected to theexternal route memory to be provided, a switching device being furtherprovided, which optionally activates the external or internal routeguidance device during route guidance, depending on whether theapparatus of locomotion is inside or outside the range of the internaldigital map.

This has the advantage that a hybrid navigation system is available, inwhich the detailed data of the internal digital map are used, as far aspossible, for route guidance, and only in ranges lying outside theinternal digital map route guidance is used on the basis of anexternally stored digital map. Thereby, according to the presentinvention, the advantages of an autonomous navigational system, namely,a high route guidance accuracy are unified with the advantages of anoff-board navigational system, namely, no range limitation based on thedigital map. At the same time, the disadvantages of an autonomousnavigational system, namely, conducting navigation exclusively withinthe internally stored map, as well as the disadvantages of an off-boardnavigational system, namely, high transmission costs due to the largedata volumes to be transmitted, are avoided. Thus, the user hasavailable to him the advantages of the off-board navigational system andthe autonomous navigational system under a uniform operating surfacehaving the best possible functions of each part.

In another embodiment of the present invention, the internal routememory and the external route memory are combined in one single memory.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic block diagram of a preferred specificembodiment of a navigational system according to the present invention.

FIG. 2 shows a segment of an internal digital map of the navigationalsystem of FIG. 1.

FIG. 3 is a first illustration of various communications steps orcommunications sequences between a navigational system and an off-boardnavigational system.

FIG. 4 is a second illustration of various communications steps orcommunications sequences between a navigational system and an off-boardnavigational system.

FIG. 5 is a third illustration of various communications steps orcommunications sequences between a navigational system and an off-boardnavigational system.

DETAILED DESCRIPTION

For the preferred exemplary embodiment of navigational system accordingto the present invention, illustrated in FIG. 1, an internal digital map101 is provided. With the aid of a position finding device 102,furnished with diverse sensors such as a GPS antenna, tacho signal, thevehicle position is assigned with great accuracy to a section of digitalmap 101 if the vehicle is in the network stored in the map. A traveldestination can be input to the navigational system via an input device103. This is verified via a destination memory 104 and possiblyidentified as pertaining to the internal digital map 101. Thedestination input memory 104 and internal digital map 101 areexpediently stored in the same storage medium, such as a CD-ROM.Thereupon a routing algorithm 105 calculates an internally calculatedroute or portion of a route from the position of the vehicle or from astarting location to the travel destination and stores this route in aninternal route memory 106. The starting location does not necessarilyhave to match the instantaneous location of the motor vehicle. Forexample, the vehicle moves during the route interrogation, so that aftera finished route calculation and route transmission the motor vehiclehas already arrived at a position displaced from the starting location.

By way of a continuously performed comparison of the vehicle positionregistered by the position finding device 102 with the stored route, andwith the aid of digital map 101, internal route guidance algorithm 107reads out the travel route, the vehicle position and also traveldirections to the destination, via a read-out device 108. This processis continuously repeated until route guidance is broken off or thedestination is reached. In addition, a remote data transmission device109 is provided for exchanging data with a traffic telematics center viacommunications networks 201. Using data received in such a way abouttraffic jams, routing algorithm 105 generates routes for detouring thetraffic jams. The center or the off-board navigational system includesan external digital map 301, an external routing algorithm 302, as wellas an input/output function 303, for instance, a device for remote datatransmission for the input of the start and destination position as wellas the output of the calculated route. In the center, data about actualand predicted traffic disruptions are used for seeking out routes,optionally using a dynamizing function. A route or portion of a routecalculated externally by the off-board navigational system is enteredinto an external route memory 110. Here the route guidance proceeds withits own external route guidance algorithm 111.

In the hybrid navigational system according to the present invention,input device 103 and destination input memory 104 are broadened in sucha way that not only destinations can be input to internal digital map101. At the beginning of the route guidance one can then choose amongthe possibilities “autonomous route guidance”, “off-board routeguidance” and “hybrid route guidance”. To do this, both internal routememory 106 (for autonomous route portions) and external route memory 110(for off-board route portions) are kept available. Furthermore, internalroute guidance algorithm 107 (map-based) and external route guidancealgorithm (111) (off-board, e.g. based on GATS) should be carried out induplicate. While driving, at interchange nodal points, using a switchingdevice 112 of the hybrid system, which, for example, may be designed asa software switch, switching takes place from the autonomous to theoff-board route guidance and back. The output device 108 and thecommunications device 109 can be used in both operating modes.

For the use in common of output device 108, both the autonomous and theoff-board navigation work in a “turn by turn” method. Using such amethod, when approaching a crossing, for instance, the drivingdirections create graphic or speech output comments on the actions to beperformed (“take next right turn to B8”, “take this right turn to B8”).

FIG. 2, for example, shows an internal digital map 101 in the vehicle,containing nodes K1 to K4 and edges K12, K13, K24 and K34. These formthe area in which navigation can be autonomous. Furthermore, sixoff-board referable nodes Z1 to Z6 are shown. Using appropriatesoftware, for example, such as look-up tables, the nodes K1 to K4 arerecognized as being respectively identical to Z1 to Z4. For example,after off-board calculation of a direct route from Z1 to Z2, this isrecognized internally in the vehicle as being identical to theautonomously calculable route from K1 to K2 which runs along edge K12.

If the navigational system is on a planned route guidance from K1 or Z1to K2 or Z2, software switch 112 switches from the internal routeguidance device 107 to external route guidance device 111 at any desiredpoint, and back. For this, both route guidance devices or algorithms107, 111, are active simultaneously, are supplied with data by positionfinding device 102, and, during the trip, sections already passed in therespective route memories 106 or 110 are marked as passed or arecanceled. Here, of particular advantage is an automatically executedchange from autonomous to off-board at interchange nodal points at whichthe area of the internal digital map 101 is left. This could happen, forexample, in the following case. A route from K1 or Z1 to Z6 is beingplanned. A corresponding route cannot be planned or calculated in theautonomous system since Z6 is not contained in internal digital map 101.Off-board, the route Z1>Z2>Z4>Z6 would be calculated. By evaluation ofsimilarities this route is analyzed. Since Z1 and Z4 can be assigned tomap nodes K1 and K4, an internal route portion K1>K2>K4 is internallycalculated and stored in the autonomous route memory 106. What is more,software switch 112 is finished with a rule such that, upon reception ofroute portions calculated off-board, these route portions lying ininternal digital map 101 are recognized and autonomous route portionsare calculated for them. Then, if on one section of the route bothmethods are possible, in an advantageous way the autonomous method ispreferably used. Use of the internally calculated route portions permitsmore precise driving instructions through map-based position finding. Inaddition, the performance characteristics for restoring to the plannedroute, in this case, are more convenient because of the knowledge of theroad network by internal digital map 101. This is relevant in case of adeliberate or unintentional branching off from the planned route. Whenit is recognized that no possibility of autonomous route guidance existsany longer, the switch 112 switches to the off-board route. In theexample described, in the hybrid navigational system according to thepresent invention, when conducting a navigation from Z1 to Z6, thisleads to the route worked out as follows: K1>K2>K4; switch fromautonomous to off-board; Z4>Z6.

Analogously, this mechanism in reverse can also be used when leaving anoff-board road portion. On the return trip from Z6 to K1, at node Z4 orK4 the possibility of autonomous route calculation would be recognized.Then the route would be as follows: Z6>Z4; switch from off-board toautonomous; K4>K2>K1.

Since the transmission of off-board routes generates communicationscosts and transmission time, when requesting route calculations, it isadvantageous to exclude from the calculations those portions where theroute can be autonomously calculated. To do this, for each destinationcontained in destination input memory 104 and not in internal digitalmap 101, an accompanying network transitional nodal point is stored. Forexample, if Z6 is input as the destination, K4 will be found as theaccompanying transition point, because it has been stored as such in thedestination input memory 104. The route from K1 to K4 is thenautonomously calculated, and the route from Z4 to Z6 is requested for anoff-board calculation. FIG. 3 shows a corresponding sequence. In FIGS. 3through 6, 10 designates the navigational system on the vehicle, 12designates a message transmitted via data communications device 109 and14 designates the off-board navigational system. At 16 the memorycontent of the destination input memory 104 is used to locate K4 as thelocal transition nodal point for Z6. At 18, a route from Z4 to Z6 isrequested. At 20, the route Z4 >Z6 is calculated in off-board navigationsystem 14. At 22 the route 24 >26 is transmitted from the off-boardnavigational system 14 to the navigational system 10 in the vehicle. At24 the internal route portion K1>K4 is calculated and route guidancestarts at 26.

Alternatively, in a separate communications step, the interchange nodalpoints are negotiated between the hybrid navigational system 10 and theoff-board navigational system 14 with the aid of a data protocol, in thelight of geographical descriptions of nodes lying outside the digitalmap, as shown in FIG. 4. Here, for example, the assignment of theinterchange nodal point K4 to the destination Z6 is not stored indestination input memory 104. Instead, as seen in FIG. 4, after input ofdestination Z6 via remote data transmission 28, the destination isidentified in the off-board navigational system 14 at 30, and theapproximate position of destination Z6 is transmitted back to thevehicle at 32, and then the next nearest interchange nodal point K4 isassigned there at 34 with the aid of a corresponding assignmentalgorithm.

If internal digital map 101, present in navigational system 10 is alsoin device 14 used for the off-board calculation, then it is sufficientfor the identification of the interchange nodal point, as illustrated inFIG. 5, to introduce into the route calculation inquiry 18 controlinformation having an identification possibility of the version ofinternal digital map 101. This information is then used off-board inorder to identify the transition nodal points at 36. For instance, theinquiry 18 may be for a route from Z1 to Z6 using digital map V1. Then,in communications step 38, route Z4 to Z6 is transmitted by theoff-board navigational system 14 to the internal navigational system 10,and the message is given that an internal route calculation has to bemade up to K4. This is done in 24, and in 26 route guidance startsagain.

Alternatively, the control information can also include a list ofpossible transition points created in hybrid navigational system 10. Theoff-board navigational system 14 then selects the interchange nodalpoint to be used. FIG. 6 shows a corresponding sequence for getting fromK1 to destination Z5. In communications step 40, Z5 is transmitted asdestination to the off-board navigational system 14. In step 42 theposition of Z5 is determined, and in communications step 44 it istransmitted to internal navigational system 10. In step 46, the nodes K2and K3 are identified as possible interchange nodal points, and incommunications step 48 (this is) transmitted to the off-boardnavigational system 14. In step 50, the route Z2 to Z5 is calculated andin communications step 52 this route, together with interchange nodalpoint K2, is transmitted to the internal navigational system 10. Thisdetermines that an internal route portion from K1 to K2 has to becalculated, which takes place in step 54.

The coding of the interchange nodal points includes, for example,geocodes according to GATS, TMC locations according to prENV 12313-3 orERTICO ILOC's. In an alternative specific embodiment, route memories 106and 110 are combined into a single one. In autonomously “drivable”portions indications are made there as to connection to its own digitalmap, and in “off-board” portions as to corridors corresponding to GATSprotocol.

The realization of a hybrid system according to the present inventionwill be described using the example of a navigational system havingdynamic APS (dynAPS). The destination input takes place there, either inthat the destinations are input, via an input device, in the sequence“city”, possibly “city part”, “street name”, “intersection or housenumber”, by spelling and selection from lists or combinations of these.The possible destinations are taken from a destination input memory 104on the CD-ROM having internal digital map 101. For the following twoexamples it is assumed that the beginning vehicle location is Cologne,the destination is Paris, and a CD-ROM containing the German roadnetwork has been inserted in the vehicle.

In order to make possible the hybrid route guidance to selecteddestinations outside internal digital map 101, this destination inputmemory 104 is enlarged by additional data, cf. FIG. 4. For the entryParis (France), in the destination input memory 104 of the CD-ROM, listsare stored of possible transitional nodal points and rules for theirselection. Let us say that, in a Germany CD-ROM and a vehicle location“North Rhine Westphalia” the interchange nodal point “A44Aachen-Lichtenbusch” is selected. This occurs without the driver beingable to recognize it. After the input of the destination, say, thedriver has selected from the navigational settings the function“Telematic/Hybrid Route”. If this setting has not taken place(autonomous route), after the selection of the destination and start ofthe route guidance an error message appears: “For this destination,travel recommendations can only be given using hybrid route guidance”.When the setting is made with hybrid route guidance, a screen outputtakes place: “Route search via traffic telematics is running”. Via a GSMmobile radio net there follows a route inquiry with the aid ofpossibilities of short message service present in dynAPS. The vehiclereceives as reply a route list assembled according to GATS, from theborder crossing Aachen-Lichtenbusch to the specified street withinParis. The list is constructed in view of the driving maneuvers thatwill need to be executed. For instance, on the trip to Paris it containsthe changes of expressways in the area of Liege. During the inquiry, theautonomously calculable portion of the route is calculated in dynAPS.When both portions are at hand, route guidance can begin.

In dynAPS, the distance from the next driving maneuver is shown eachtime on a screen. At the approach to the place of the maneuver, apictogram of the place of this maneuver appears, along with the enteredexpected travel path. At the approach to the expressway cloverleafAachen, coming from Cologne on the A4, this would be first the distanceto the cloverleaf Aachen, and, on closer approach, an image signaling“exit right”. The driving instructions are also spoken at the approach.

The approach to the border crossing Aachen-Lichtenbusch would besignaled in a similar way, “before long, drive straight ahead”. Uponpassing the border, autonomous route guidance is switched to off-boardroute guidance without this being noticed by the driver. The data forassignment to the driving instructions and the vehicle position for theplanned route no longer come aided by digital map 101 on the CD-ROM butfrom route information received at the GATS center. The driver onlybecomes aware that he has left the area of the digital map from lessprecise driving instructions, because of less accurate position finding,and a different performance at exiting from the planned route. After theborder crossing, the “normal” dynAPS would create the message “OFF MAP”.

In the next example there will be shown a trip, using a hybrid APS, fromCologne to Steinfurt, Burgsteinfurt District, Wemhöferstiege. After thedestination input, it is realized that the trip destination lies in aplace in which only the center, but not the individual streets in theresidential areas have been digitized. Support for the destinationinput, as in the previous example, by the deposit of data in thedestination input memory, is not possible here. At a route inquiry viaSMS, the hybrid APS transfers to the GAT center not only the startingposition and the desired trip destination, but also an identification ofthe inserted CD-ROM (data volume, version), cf. FIG. 5. The GATS centercan only recognize to which transition nodal point of the internaldigital map 101 direction is to be made. A point is found here, astransitional nodal point, between the crossing B54/B54 n, at the westernentrance to the Burgsteinfurt District, and the point lying on B54 andstored on the CD-ROM as Burgsteinfurt/Center. From the crossing B54/B54n and past the transitional point the route to be taken in Burgsteinfurtto Wernhöferstiege is calculated at the center and transmitted to thevehicle. There, now, the route is calculated autonomously as far as theinterchange point. Furthermore, the off-board route is entered intoroute memory 110. Switching from autonomous to hybrid route guidance isprepared after passing the crossing B54/B54 n. The driving maneuverthere is still executed under control of the autonomous route guidance.The next driving maneuver, “turn right” at the interchange nodal pointis already taken from the off-board route. However, it is still turnedon by the route guidance algorithm 105. Only after the maneuver executedat the interchange nodal point does off-board route guidance algorithm111 take over directing.

After passing the interchange nodal point, the “normal” dynAPS wouldcreate the message “OFF ROAD”. Indeed, the generation of a drivinginstruction, “turn right” for leaving the digitized street net would notbe possible.

In summary, the present invention relates to a navigational system fornavigating in a vehicle, a route stored in a navigational system fornavigating being composed of route sections calculated, proportionately,in the vehicle using data of a digital map 101 (autonomously) and asreceived from an external routing 302 (off-board). For this, externallydetermined portions do not necessarily have to be contained in digitalmap 101 used in the vehicle for the routing. It is further advantageousto make the design such that the switching between the centrally andautonomously calculated sections takes place either controlled by auser, or, if desired, unobserved in the background, the individual routesegments being furnished with control data controlling the switching,for automatic switching in the background, in the route memory.

It is especially advantageous that a uniform user interface is used forthe output of driving instructions and of the route, and indeedindependently of which type of route section is just being passed by thevehicle. Furthermore, the dual design of route memory 106, 110 is ofadvantage, route memory 110 containing the central, externallycalculated route and the other route memory 106 containing theautonomous, internally calculated route, and, based on control data whenneeded, being switched from one to the other route memory. Alsoadvantageous is the transmission of the externally determined portionsvia a remote data transmission device 109, such as by data radio in amobile radio net such as SMS transmission in GSM. Here, the transmissioncan be directed both unidirectionally to the vehicle (broadcast) or itcan use bidirectional data traffic. The externally calculated portionscan be transmitted with the aid of GATS geocodes, with the aid of TMClocations, with the aid of ERTICO ILOC's or by other methods, accordingto GATS Appendix 5.3.1 and 1151.3.2. Alternatively, the externallycalculated route can be fed in via a serial line-bound or infraredinterface, a network interface, or by using a storage medium that isexternally written and read in the navigational system (diskette, PCMCIAcard, . . . ). Additionally advantageous is the automatic creation ofcontrol data in such a way that, at receipt of an externally determinedroute, those portions of the route which are unequivocally assignable inthe digital map located in the vehicle, are replaced after the receiptby portions calculated in the vehicle.

Transmission of data via the digital map present in the vehicle isadvantageous, so as to be able to use this version of the information inthe external route calculation, whereby to determine externally onlythose portions of the route not calculable in the vehicle, and totransmit these into the vehicle, while the remaining portions arecalculated in the vehicle. Advantageous, also, is the transmission oflists of possible entry and exit points of the vehicle to the center,for the route portions calculated there, suitable entry and exit pointsbeing selected in the center and transmitted to the vehicle for eachcorresponding portion of the route Also advantageous is the transmissionof entry points and exit points which are obtained in the vehicle fromgeographic or other information concerning vehicle position and desireddestinations, so as to let the external route calculation calculate onlythe sections from the starting position to the first entry point, orfrom the last exit point to the trip destination, or from one or moreexit points lying on the route to the corresponding entry pointsoccurring after them.

In those situations in which the vehicle leaves the area of digitizedmap 101, an inquiry for calculation of an external route calculation iscreated automatically or manually, and the result of this calculation isused for feedback into digitized street net 101 or for route guidance tothe trip destination. When route guidance with the aid of the digitizedmap 101 is possible, switching takes place in an advantageous mannerfrom route guidance with the aid of an external route to autonomouslycalculated route guidance. When route guidance with the aid of digitizedmap 101 is no longer possible, and the vehicle position can be assignedto the externally received route, then, in an advantageous manner,switching takes place from autonomous route guidance to the externalroute.

What is claimed is:
 1. A method for navigating an apparatus oflocomotion in accordance with a route including nodal points from one ofa starting point and an instantaneous location to a destination in acase in which at least one of the nodal points of the route to becalculated is not contained in an internal digital map stored internallyin a navigational system, the method comprising the steps of:calculating that part of the route including exclusively nodal points ofthe internal digital map in accordance with an internal routingalgorithm on the basis of the internal digital map to produce aninternally calculated route portion; calculating that part of the routenot including those of the nodal points stored in the internal digitalmap in accordance with an external routing algorithm to produce anexternally calculated route portion on the basis of an external digitalmap stored externally with respect to the navigational system;determining transitional nodal points from the externally calculatedroute portion to the internally calculated route portion; and performingone of the steps of: causing an internal route guidance algorithm of thenavigational system to execute a route guidance on the basis of theinternally calculated route portion, and causing an external routeguidance algorithm to execute the route guidance on the basis of theexternally calculated route portion.
 2. A method for navigating anapparatus of locomotion in accordance with a route including nodalpoints from one of a starting point and an instantaneous location to adestination in a case in which at least one of the nodal points of theroute to be calculated is not contained in an internal digital mapstored internally in a navigational system, the method comprising thesteps of: first calculating the route completely in accordance with anexternal routing algorithm; transmitting the completely calculated routeto the navigational system; subsequently calculating that portion of theroute that includes exclusively those of the nodal points in theinternal digital map in accordance with an internal routing algorithm;and replacing that portion of the completely calculated routecorresponding to those of the nodal points exclusively in the internaldigital map with that portion of the route calculated in accordance withthe internal routing algorithm.
 3. The method according to claim 1,wherein: the internal routing algorithm first generates the internallycalculated route portion, the internal routing algorithm transmits dataconcerning still missing portions of the route to the external routingalgorithm, and the external routing algorithm calculates only the stillmissing portions of the route and transmits the calculated still missingportions of the route to the navigational system.
 4. The methodaccording to claim 3, wherein: the still missing portions include stillmissing nodal points and interchange nodal points.
 5. The methodaccording to claim 1, wherein: the internally calculated route portionis stored in the navigational system in an internal route memory, andthe externally calculated route portion i s stored in an external routememory.
 6. The method according to claim 5, further comprising the stepsof: on reaching an interchange nodal point, switching from the internalroute guidance algorithm to the external route guidance algorithm whenthe apparatus of locomotion leaves a range of the internal digital map;and on reaching the interchange nodal point, switching from the externalroute guidance algorithm to the internal route guidance algorithm whenthe apparatus of locomotion reaches the range of the internal digitalmap.
 7. The method according to claim 5, further comprising one of thesteps of: during the route guidance, identifying in the internal routememory and the external route memory as one of taken care of and passedthose of the nodal points corresponding to those portions of the routethat are one of already reached and already passed, the identifying stepbeing performed independently of which one of the internal routeguidance algorithm and the external route algorithm is currently active;and during the route guidance, canceling in the internal route memoryand the external route memory those of the nodal points corresponding tothose portions of the route that are one of already reached and alreadypassed, the canceling step being performed independently of which one ofthe internal route guidance algorithm and the external route algorithmis currently active.
 8. The method according to claim 1, wherein: thenodal points include internal nodal points and external nodal points,the internal nodal points stored in the internal digital map and theexternal nodal points that are outside of a range of the internaldigital map are stored in a destination input memory of the navigationalsystem, and at least one interchange nodal point is stored in theinternal digital map for predetermined external nodal points.
 9. Themethod according to claim 1, further comprising the step of: in aseparate communication between the navigational system and an off-boardnavigational system that executes the external routing algorithm andstores the external digital map, determining interchange nodal points inaccordance with a data protocol in view of geographical descriptions ofthose of the nodal points lying outside the internal digital map. 10.The method according to claim 1, further comprising the step of: afteran input of a destination location lying outside a range of the internaldigital map, causing the navigational system to transmit the inputdestination location and a version number of the internal digital map toan off-board navigational system; causing the off-board navigationalsystem to execute the external routing algorithm and to store theexternal digital map; causing the off-board navigational system todetermine an interchange nodal point from the input destination locationand the version number of the internal digital map; causing the externalrouting algorithm to calculate the externally calculated route portionfrom the interchange nodal point to the input destination location; andtransmitting the externally calculated route portion to the navigationalsystem.
 11. The method according to claim 1, further comprising thesteps of: causing the navigational system to transmit a list of possibleinterchange nodal points to an off-board navigational system; causingthe off-board navigational system to execute the external routingalgorithm and store the external digital map; causing the off-boardnavigational system to select at least one suitable interchange nodalpoint according to the externally calculated route portion; and causingthe off-board navigational system to transmit the at least one suitableinterchange nodal point to the navigational system along with theexternally calculated route portion.
 12. The method according to claim1, wherein: a calculation of the externally calculated route portionoccurs when the apparatus of locomotion leaves an area of the internaldigital map.
 13. A navigational system for an apparatus of locomotion,comprising: an internal route memory; an internal route guidance deviceconnected to the internal route memory; an internal digital map; a datacommunications device for communicating with an external off-boardnavigational system; an external route memory connected to the datacommunications device; an external route guidance device connected tothe external route memory; and a switching device for alternativelyactivating one of the external route guidance device and the internalroute guidance device during a route guidance, depending on whether theapparatus of locomotion is one of within and outside a range of theinternal digital map.
 14. The navigational system according to claim 13,wherein: the apparatus of locomotion includes one of a motor vehicle, aship, and an airplane.
 15. The navigation system according to claim 13,wherein: the internal route memory and the external route memory arearranged in a single memory.